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Flashcards in Calcium Deck (22):

describe the location of calcium in the body

  • 99% in bone
  • 1% in body fluids
    • 50% is free in ionized form
    • rest is bound to proteins


describe the organs involved in maintaining Ca within physiologic range

  • gut absorption 
  • bone uptake and release
  • kidney Ca reabsorption 


Ca in bone exists in 2 pools:

  1. readily exchangable pool
  2. stable pool


describe how physiologic pH changes impact Ca levels

  • alkalotic pH 
    • protein charge becomes more negative
    • there is increase in Ca binding
    • alkalosis decreases plasma [Ca]
  • acidic pH
    • protein charge is less negative
    • there is less Ca binding
    • acidosis increases plasma [Ca] 


name factors that alter blood Ca levels

  • DECREASE in Ca levels
    • nephrotic syndrome
    • malnutrition
    • liver disease
  • INCREASE Ca levels
    • multiple myeloma


describe phosphate distribution in the body

  • 86% is in bone
    • elemental form
  • 13-14% in ICF
    • organic form


______ is not important for Ca regulation in humans but important in fetus

calcitonin is not important for Ca regulation in humans but important in fetus


describe PTH

  • synthesized and secreted by chief cells in the parathyroid
  • the most important regulator of ECF Ca


describe trigger for release of PTH

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describe the mechanism of PTH suppression

high levels of Ca INHIBIT PTH release

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describe the action of PTH on bone

indirect action on osteoclast

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describe the aciton of PTH on kidneys

  • increase renal tubular reabsorption of Ca in the distal tubules
  • decrease renal tubular reabsorption of PO4 (phosphate tinkling hormone)
  • indirectly increase intestinal absorption of Ca
    • via Vit. D


describe vitamin D, where it's obtained and what is needed to make it active

  • steroid
  • formed in the skin or obtained in diet
  • requires PTH to reach its active form (1,25-dihydroxycholecalciferol/calcitriol)


describe the cutaneous synthesis of calcitriol

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describe calcitrol (vit D) signalling pathway

intracellular receptor (it's a steroid)


describe the effect of vit D on duodenal cell

  • calbindin helps to maintain low intracellular calcium levels in order to pump more Ca in

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describe hypocalcemia

  • increases membrane excitability
    • paresthesias
    • hypocalcemic tetany
    • Chovstek's sign of facial twitching
    • Trousseau's sign when hand goes into tetany
    • EKG shows prolonged QT interval


describe hypercalcemia


describe primary hyper-parathyroidism

  • usually due to parathyroid tumor
  • excess PTH causes:
    • increased Ca and phosphaturia
    • polyuria and calciuria forms kidney stones
    • develop cystic lesions in the bone
  • "stones, bones and abdominal groans"


describe secondary hyperparathyroidism

  • causes:
    • diet deficient in vit. D
    • increased need for Ca (pregnancy/lactation)
  • characterized by:
    • increased serum PTH
    • decreased to normal Ca 
    • decreased serum phosphate levels but normal to increased urine phosphate levels


describe rickets and osteomalicia

  • causes:
    • Vitamin D deficiency
  • decreased levels of Ca and PO4 in ECF
  • characterized by deminiralization of the osteoid matrix
    • children = rickets
    • adults = osteomalicia


describe primary hypoparathyroidism

  • cause = accidental removal of glands during thyroid/neck surgery
  • characterized by:
    • low Ca and high plasma phosphate levels
    • tetany due to increased muscle excitability
    • decreased Ca can lead to death